On Tue, Sep 13, 2022 at 07:14:56PM +0200, Jann Horn wrote: > As the subject says, there's a race between d_path() (specifically > __prepend_path()) looking at mnt->mnt_ns with is_anon_ns(), and > do_move_mount() switching out the ->mnt_ns and freeing the old one. > This can theoretically lead to a use-after-free read, but it doesn't > seem to be very interesting from a security perspective, since all it > gets you is a comparison of a value in freed memory with zero. ... with d_absolute_path() being the only caller that might even theoretically care. Anyway, shouldn't be hard to deal with - adding rcu_head to struct mnt_namespace (anon-unioned with e.g. ->list) and turning kfree() in free_mnt_ns() into kfree_rcu() ought to do it...
